Academic interests

I am working in a research group headed by Prof. Anders M. Fjell and Prof. Kristine B. Walhovd. We strive to understand the complex and dynamic relationship between alterations in the brains structural make-up and its functional manifestations in normal development and aging, as well as following discontinuity in the normal development trajectories due to for instance disease. To this end, we use magnetic resonance imaging (MRI), including diffusion tensor imaging, electroencephalography/event-related potentials, and various cognitive-behavioural tasks. Our current and planned research projects also include genetic data in order to investigate the influence of genetic variance on cognitive and brain-based phenotypes.

Higher education and employment history

Employment

2010-present PhD Research Fellow (The Research Council of Norway), Center for the Study of Human Cognition, Department of Psychology, University of Oslo

2008-2009 Student Research Fellow (part time) (The Research Council of Norway), Department of Psychology, University of Oslo

2007-2008 Student Research Fellow (full time) (The Research Council of Norway), Department of Psychology, University of Oslo

There is a growing realization that early life influences have lasting impact on brain function and structure. Recent research has demon- strated that genetic relationships in adults can be used to parcellate the cortex into regions of maximal shared genetic influence, and a major hypothesis is that genetically progr ammed neurodevel opmental events cause a lasting impact on the organization of the cerebral cortex observable decades later. Here we tested how developmental and lifespan changes in cortical thickness fit the underlying genetic organi- zational principles of co rtical thickness in a longitudinal sample of 974 participants between 4.1 and 88.5 y of age with a total of 1,633 scans, including 773 scans from children below 12 y. Genetic clustering of cortical thickness was based on an independent dataset of 406 adult twins. Developmental and adult age- related changes in cortical thick- ness followed closely the genetic organization of the cerebral cortex, with change rates varying as a functi on of genetic similarity between regions. Cortical regions with overlapping genetic architecture showed correlated development al and adult age change trajectories and vice versa for regions with low genetic overlap. Thus, effects of genes on regional variations in cortical thickness in middle age can be traced to regional differences in neurodevelopmental change rates and extrap- olated to further adult aging-related cortical thinning. This finding suggests that genetic factors contribute to cortical changes through life and calls for a lifespan perspective i n research aimed at identifying the genetic and environmental determinants of cortical development and aging.

Advances in neuroimaging techniques have recently provided glimpse into the neurobiology of complex traits of human personality. Whereas some intriguing findings have connected aspects of personality to variations in brain morphology, the relations are complex and our current understanding is incomplete. Therefore, we aimed to provide a comprehensive investigation of brain–personality relations using a multimodal neuroimaging approach in a large sample comprising 265 healthy individuals. The NEO Personality Inventory was used to provide measures of core aspects of human personality, and imaging phenotypes included measures of total and regional brain volumes, regional cortical thickness and arealization, and diffusion tensor imaging indices of white matter (WM) microstructure. Neuroticism was the trait most clearly linked to brain structure. Higher neuroticism including facets reflecting anxiety, depression and vulnerability to stress was associated with smaller total brain volume, widespread decrease in WM microstructure, and smaller frontotemporal surface area. Higher scores on extraversion were associated with thinner inferior frontal gyrus, and conscientiousness was negatively associated with arealization of the temporoparietal junction. No reliable associations between brain structure and agreeableness and openness, respectively, were found. The results provide novel evidence of the associations between brain structure and variations in human personality, and corroborate previous findings of a consistent neuroanatomical basis of negative emotionality.

People show consistent differences in their cognitive and emotional responses to environmental cues, manifesting e.g. as variability in social reward processing and novelty seeking behavior. However, the neurobiological foundation of human temperament and personality is poorly understood. A likely hypothesis is that personality traits rely on the integrity and function of distributed neurocircuitry. In this diffusion tensor imaging (DTI) study, this hypothesis was tested by examining the associations between reward dependence (RD) and novelty seeking (NS), as measured by Cloninger’s Temperament and Character Inventory (TCI), and fractional anisotropy (FA) and mean diffusivity (MD) as DTI derived indices of white matter microstructure across the brain. The results supported the hypothesis. RD was associated with WM architecture coherence as indicated by a negative correlation between RD and FA in frontally distributed areas including pathways connecting important constituents of reward related neurocircuitry. The associations between RD and FA could not be explained by age, sex, alcohol consumption or trait anxiety. In contrast, no effects were observed for NS. These findings support the theory that WM fiber tract properties modulate individual differences in social reward processing.

A core brain network is engaged in remembering the past and envisioning the future. This network overlaps with the so-called default-mode network, the activity of which increases when demands for focused attention are low. Because of their shared brain substrates, an intriguing hypothesis is that default-mode activity, measured at rest, is related to performance in separate attention-focused recall and imagination tasks. However, we do not know how functional connectivity of the default-mode network is related to individual differences in reconstruction of the past and imagination of the future. Here, we show that functional connectivity of the default-mode network in children and adolescents is related to the quality of past remembering and marginally to future imagination. These results corroborate previous findings of a common neuronal substrate for memory and imagination and provide evidence suggesting that mental time travel is modulated by the task-independent functional architecture of the default-mode network in the developing brain. A further analysis showed that local cortical arealization also contributed to explain recall of the past and imagination of the future, underscoring the benefits of studying both functional and structural properties to understand the brain basis for complex human cognition.

Context Emotional, cognitive, and behavioral response patterns underlying temperament and personality are established early and remain stable from childhood. Anxiety-related traits are associated with psychiatric disease and represent predisposing factors for various affective disorders, including depression and anxiety. Emotional processing relies on the structural and functional integrity of distributed neuronal circuits. Therefore, anxiety-related personality traits and associated increased risk of psychiatric disease might be rooted in structural variability in large-scale neuronal networks. Objective To test the hypothesis that individuals with high scores on the harm avoidance (HA) subscale of the Temperament and Character Inventory show reduced white matter (WM) structural integrity in distributed brain areas, including corticolimbic pathways involved in emotional processing and reappraisal. Design Healthy participants completed the Temperament and Character Inventory and underwent diffusion tensor imaging. Tract-based spatial statistics were used to examine the associations between HA and WM integrity across the brain. Setting Center for the Study of Human Cognition, Department of Psychology, University of Oslo, Oslo, Norway. Participants A total of 263 healthy adults aged 20 to 85 years recruited through newspaper advertisements. Main Outcome Measure Neuroimaging diffusivity indexes of brain WM microstructure, including fractional anisotropy, mean and radial diffusivity, and their associations with HA. Results In line with our hypothesis, increased HA was associated with decreased fractional anisotropy and increased mean and radial diffusivity in major WM tracts, including pathways connecting critical hubs in a corticolimbic circuit. There was no evidence of modulating effects of sex, degree of subclinical depression, alcohol consumption, general intellectual abilities, or years of education. Conclusions Increased HA is associated with decreased WM microstructure, implying that structural connectivity modulates anxiety-related aspects of personality. Decreased WM integrity reflects increased susceptibility to psychiatric disease and represents a promising biomarker that might ultimately facilitate targeted pharmacological and psychological interventions and treatment of disease.

Efficient attention is pivotal for cognitive functioning, and individual differences in attentional functions are likely related to variations in structural properties of the brain. Attention is supported by separate processes, and models of the relationship between 10 attention and brain structure must take this into account. The Attention Network Test (ANT) yields behavioral measures of 3 independent attentional components: executive control (EC), alerting, and orienting. EC relates to resolving cognitive interference, alerting refers to continuous maintenance of a vigilant state, and orienting to selection of and orienting toward sensory information. Evidence from functional euroimaging studies suggests that the ANT components recruit different cortical networks. However, the structural correlates are not established. Therefore, ANT scores were correlated with cortical thickness across the 20 brain surface in 268 healthy adults spanning 20-84 years of age. Specific correlations were found between cortical thickness and EC and alerting in regions implicated by functional euroimaging and lesion studies, including anterior cingulate, lateral prefrontal, and right inferior frontal gyri for EC and parietal areas for alerting.The brain-behavior correlations were relatively stable across adulthood, indicating that factors influencing cortical maturation rather than aging-related atrophy specifically were instrumental in shaping the structural foundation for visuospatial attention in adults.

Cortical thickness decreases from childhood throughout life, as estimated by magnetic resonance imaging (MRI). This monotone trajectory does not reflect the fundamentally different neurobiological processes underlying morphometric changes in development versus aging. We hypothesized that intracortical gray matter (GM) and subjacent white matter (WM) T1-weighted signal intensity would distinguish developmental and age-related changes in the cortex better than thickness. Intracortical GM and subjacent WM signal intensity and cortical thickness was measured across the brain surface in a healthy life span sample (n = 429, 8–85 years). We also computed the relaxation rate of T2* (R2*) from multiecho sequences and mapped intracortical GM and subjacent WM values to the surface to delineate age-related variability in R2* and to adjust the T1 signal intensity for possible confounds of accumulated iron. While monotone age-related reductions in thickness were found, both intracortical GM and subcortical WM signal intensity showed inverted U patterns with peaks from eight to approximately 30 years of age. The spatial pattern of intracortical neurodevelopment followed a posterior–anterior gradient, with earliest maturation of occipital visual cortices and most protracted in superior frontal regions. From 50 s and 60 s, substantial signal reductions were observed in several regions, including the insula, cingulate, and inferior temporal gyrus. R2* showed similar patterns but peaked much later than the T1-weighted signal intensity measures. The results are presented as animations yielding detailed depictions of the dynamic regional variability in cortical neurodevelopment and aging and demonstrate that cortical thickness and T1-weighted signal intensity are sensitive to different cortical maturational and aging-related processes.

Magnetic resonance imaging volumetry studies report inverted U-patterns with increasing white-matter (WM) volume into middle age suggesting protracted WM maturation compared with the cortical gray matter. Diffusion tensor imaging (DTI) is sensitive to degree and direction of water permeability in biological tissues, providing in vivo indices of WM microstructure. The aim of this cross-sectional study was to delineate age trajectories of WM volume and DTI indices in 430 healthy subjects ranging 8–85 years of age. We used automated regional brain volume segmentation and tract-based statistics of fractional anisotropy, mean, and radial diffusivity as markers of WM integrity. Nonparametric regressions were used to fit the age trajectories and to estimate the timing of maximum development and deterioration in aging. Although the volumetric data supported protracted growth into the sixth decade, DTI indices plateaued early in the fourth decade across all tested regions and then declined slowly into late adulthood followed by an accelerating decrease in senescence. Tractwise and voxel-based analyses yielded regional differences in development and aging but did not provide ample evidence in support of a simple last-in-first-out hypothesis of life-span changes.